An increasing demand for electronic equipment that is smaller, lighter, and more compact has resulted in a concomitant demand for semiconductor packages that have smaller outlines and mounting areas or “footprints.” One response to this demand has been the development of the “flip-chip” method of attachment and connection of semiconductor chips or “dice” to substrates (e.g., PCBs or lead-frames). Flip-chip mounting involves the formation of bumped contacts (e.g., solder balls) on the active surface of the die, then inverting or “flipping” the die upside down and reflowing the bumped contacts (i.e., heating the bumped contacts to the melting point) to form solder joints fusing the bumped contacts to the corresponding pads on the substrate.
In flip-chip mounting and connection methods, thermo-mechanical reliability is becoming an increasing concern of the electronics industry. Notably, the reliability of the solder joints is one of the most critical issues for successful application of such mounting and connection methods. However, solder joints formed using known methods may be prone to cracks at high-stress points due to thermal stress cycling.
Therefore, there is a need for improved solder joints and methods of forming improved solder joints for an integrated circuit.